1. Field of the Invention
The present invention relates to the fields of virology, cellular and molecular biology. More particularly, the invention relates to the development of a method for increasing the susceptibility of epithelial cells to infection by viruses and viral vectors, including viral vectors and other vectors used in the gene therapy. Thus, the invention also relates to the delivery of therapeutic genes to diseased tissues.
2. Description of Related Art
Numerous diseases exist which are the result of congenital and acquired genetic defects. Diseases resulting from congenital inherited defects include cystic fibrosis (CF) and various other genetic deficiencies. CF is a common, recessive disease characterized by decreased chloride ion permeability in epithelial tissues (Quinton, 1990). While several tissues are affected by the disease, it is chronic lung disease that causes 95% of the mortality associated with CF (Welsh et al., 1995). The CF gene product has been identified (Tsui et al., 1989) and is called cystic fibrosis transmembrane conductance regulator (CFTR). Over 800 different mutations of CFTR have been associated with clinical disease. Studies have established that transfer of the wild-type CFTR cDNA into CF epithelia corrects the characteristic CF defect in chloride ion secretion (Rich et al., 1990; Drumm et al., 1990).
Another important genetic disease is cancer. Cancer is usually the result of an accumulation of genetic damage, most of which is acquired, but some of which may be the result of congenital genetic defects. As described by Foulds (1958), cancer is usually the product of a multistep biological process, which is presently known to occur by the accumulation of genetic damage. On a molecular level, the multistep process of tumorigenesis involves the disruption of both positive and negative regulatory effectors (Weinberg, 1989). The molecular basis for human colon carcinomas has been postulated by Vogelstein and coworkers (1990) to involve a number of oncogenes, tumor suppressor genes and repair genes. Similarly, defects leading to the development of retinoblastoma have been linked to another tumor suppressor gene (Lee et al., 1987). Still other oncogenes and tumor suppressors have been identified in a variety of other malignancies.
The development of effective gene therapies therefore is critical to the treatment of chronic and progressive diseases resulting from genetic defects. Gene transfer to epithelial cells in particular would be required for treatment of numerous diseases caused by genetic defects effecting epithelial tissue. Examples of such diseases include lung cancer, tracheal cancer, asthma, surfactant protein B deficiency, alpha-1-antitrypsin deficiency and cystic fibrosis.
However, transfer of foreign DNAs into human cells in vivo has proved to be a challenging undertaking. Various viral vectors have been designed for use in gene therapy in order to deliver foreign DNA to human tissues, including retrovirus (both murine virus and lenitvirus), adenovirus, papilloma virus, herpesvirus, parvovirus and poxivirus. Non-viral vectors including naked DNA, DNA complexed with lipids, or other conjugates may be used as well. All of these vectors have been successful, but there remain various obstacles that limit the efficacy of these vectors. One of the most serious obstacles to be overcome in gene therapy is low cellular viral infection rates, and therefore low gene transfer efficiency, particularly in non-dividing cells.
Thus, there remains a need to improve the efficiency of infection of target cells, in the context of gene therapy, by various viral and non-viral vectors. With the current interest in gene therapy, the need for improving the existing gene therapy vectors is greater than ever.